cirri

1. cloud forming wispy filamentous tufted streaks or ‘mare's tails’ at high altitude (usually 5 to 13 km, 16,500 to 45,000 ft).

   long strands of high cirrus stretched across the eastern sky

   cirrus clouds

2. a slender tendril or hairlike filament, such as the appendage of a barnacle, the barbel of a fish, or the intromittent organ of an earthworm.

early 18th century (in the sense ‘tendril’): from Latin, literally ‘a curl’.